Improving towing performance/mileage?

[Bogie]

Vehicle is a 3/4 ton 1995 Chevy van with a 350, overdrive auto, and a tow package.
 
It has been suggested that I tow only in "third" gear, so as to avoid burning the thing in overdrive.
 
In "regular" driving, it gets about 15-17mpg.

In "towing" (6x12 enclosed cargo trailer with a little extra height), it gets 9.5 (speed limit) to 11.5 (55 and getting passed a lot) mpg.
 
Any suggestions?

[dch1978]

I have a 92 Chevy Ex cab pick-up.  The best I get has been up to 15 by itself, downhill.......

Yours may be the Vortec motor and they are better as per you example.  

Fuel Injector cleaner is your friend, run that every couple months and it might improve.  Check out the ignition, make sure timed right and good plugs and wires, don't remember if the 95 has a distributor, but that may need attention also.  Also tire pressure, air filter, and wax it (better BC).

DO NOT tow in overdrive, some will tell that if it does not shift down while towing that you will be OK.  This is not true, the slower engine speed does not circulate fluid sufficiently in OD and it will get hot, then it blows fluid, and now you are overheating and under fluid level, transmission gone.

I just rebuilt a transmission because of the years of abuse at 200,000.  The transmission was completely shot, the bronze and copper thrustwashers had worn through and were laying in the oil pan.

Other than that I don't know, your really not doing that bad for mileage, much better than I get with a snowmobile trailer (2 place).  Doing that it is around 6mpg for me, run the AC and its GALLONS per MILE.

Hope that helps.

DCH

[Leatherneck]

I hear the folks saying don't tow in O/D, but I chose not to observe that advice and have suffered no consequences.

My truck is a 2000 Dodge Ram 1500 with the heaviest-duty tow package available. 5.9L engine. Trailer is a two-wheeler carrying a Kubota backhoe/loader; total trailer weight 9,800 lbs.

I tow in O/D which drops the usual mileage from 17.5 (long-haul) to 15.0. I keep an eye on temps and listen for smells, etc. I've got 90,000 miles on the truck and have serviced the transmission twice. The fluid both times looked and smelled normal.

YMMV

TC

[TarpleyG]

It has been suggested that I tow only in "third" gear, so as to avoid burning the thing in overdrive.

This is true...

By "tow package" do you mean just the hardware to hook up a trailer or does that also include a transmission cooler?  If you don't have one, get one.  It may help some on gas milage and it will definitely increase the life of your transmission.

Greg

[charby]

If you are worried about fuel consumption pulling a trailer get a diesel. Plus a trailer adds a lot more air resistance so even if you pull an empty flat bed your mileage will drop.

I mostly pull my boat. It and the trailer weigh about 700lbs and my mileage drops by 25% when pulling it.

In addition to what dch1978 said:

Overdrives on a passenger vehicles and pickups are designed to get better fuel economy while not pulling a load. It basically reduces the rpm of the engine at highway speeds. While pulling a load in overdrive the transmission will up-shift and downshift when ever the rpm of the engine drops below a certain level, very easily done pulling weight even up and down really slight grades. This causes excessive wear on the transmission.

[dch1978]

Charby,

My brother got the diesel(2004 4 door Duramax), so when going to Wyoming we take that.  Four snowmbiles on the high trailer it still pulled Wasta hill in SD at 80 mph with the cruise and no overheating or down shift.

But if you are not going to be pulling a trailer 75% or more of the time I don't think the diesel is worth it.

You are looking at problems to start in cold weather, higher priced fuel than gas, plus the $5000 premium for the diesel engine over a comparable gas engine.

Daily drive to work for my brother is 10 miles to work and with that he gets around 17mpg.  2 miles per gallon take a million miles to make up the dollars difference, unless of course the fuel is red (heh heh heh).  Last time I sat and figured Dollars per Mile between his and mine on average, the diesel beat the gas by .1 CENTS, probably statistically insignificant.

If you want mileage you will have to sacrifice comfort.  Tiny vehicles, Geo metro gets like 50mpg, or drive slower.

Oh on the trailer, is it flat front or V.  The V front does slightly better, how much I can't say.  Would it be worth buying a new trailer, I kinda doubt it.

Hope this helps

disclaimer:  I am an engineering student so I tend to look at the theoritical issues and the hard numbers to make a decision.  Some say it is downfall, other not.  I used believe that diesel only belonged in a Semi (Cummins) or a tractor, a pick-up was a joke (Exposed to 6.2Litre).

PS I graduate tomorrow and need a job, anybody need an ME from Iowa State University?

DCH

[roo_ster]

dch1978:

Re Engineering Student
My company is hiring.  I can be PM'ed at THR.

Re 6.2L GM deisel
A friend of the family used to tow 6 & 7 horse trailers with a 85 3/4 ton HD chevy.  Good for 350K miles with no major work & good for 24MPH highway (no trailer @ speed limit).

I would love to have a deisel available in a compact or full sized 1/2 ton PU.

[charby]

dch

too funny, I work for ISU.

Yeah your right unless you pull a heavy trailer a lot or travel vast distances in a pickup, diesel isn't worth the extra money right now. I have a feeling that someday diesel will surpass gas engines sold in vehicles. Mostly due to oil prices and bio diesel.

-C

[Larry Ashcraft]

I would love to have a deisel available in a compact or full sized 1/2 ton PU.

My son in law tells me that GM is working on a V6 Duramax for the half ton class for 2008 or '09.  Wouldn't that be a kick!

Bogie, check you owners manual re the overdrive.  The older Fords with the AOD transmission were supposed to be locked out for towing.  My 1992 Ford had the E4OD and the manual said to use OD when towing.  I always did, and the old Ford has 180k on it now and the trans is still working fine.  I'll bet the Chevy can be used in OD as long as you have a trans cooler.

[Tallpine]

That's about the mileage that I would expect for that type of vehicle and trailer.  How heavy is the trailer?

I doubt you would get any better mileage towing in OD - it might even be worse since the engine would actually be working harder, and having to rev up and slow down as the tranny "hunts" for a comfortable gear.  Level ground with a tail wind you might get away with using OD.  But a transmission replacement/repair will cost a lot more than a little bit of gas.

I'm sure your van has a factory transmission cooler.  You could add a second cooler (in line) but I doubt you would need it.

My experience with that Chevy transmission is that it doesn't downshift soon enough on hills (though you probably don't even have the kind of hills I am talking about).  My Suburban will slow way down in high gear (not OD) on a steep mountain pass with a trailer, to about 30mph where it shifts and starts to speed up again.  But if I manually shift it down to "second" at about 45, then it will either hold that speed or even speed up with the same throttle position.  Seems to me if you are going faster with the same throttle position, then you are using less gas even though the engine is turning faster.



You could try putting bigger tires on the rear axle - so that you are always going downhill  

[Brad Johnson]

Vehicle is a 3/4 ton 1995 Chevy van with a 350, overdrive auto, and a tow package.

It has been suggested that I tow only in "third" gear, so as to avoid burning the thing in overdrive.

In "regular" driving, it gets about 15-17mpg.

In "towing" (6x12 enclosed cargo trailer with a little extra height), it gets 9.5 (speed limit) to 11.5 (55 and getting passed a lot) mpg.

Any suggestions?

You have a big and very un-aerodynamic box on wheels towing another big un-aerodynamic box on wheels. I'd say you're darn fortunate to be getting the kind of economy you are. If you want better economy that that while towing, either drive slower or get a diesel.

FYI, the reason they tell you to not tow in overdrive is because the engagement clutches in the torque converter and overdrive pack won't take the strain. You would have to save a lot of fuel to pay for a $2500 tranny.

Brad

[Bogie]

Okay. Thanks. I'm also guessing that there's not a lot of air filter/chip type stuff I could do either...

[Larry Ashcraft]

Okay. Thanks. I'm also guessing that there's not a lot of air filter/chip type stuff I could do either...

Anything you can do to increase the performance of the engine would help.  K&N filter, less restrictive exhaust, etc.

My 1975 Ford F150 with a 390, granny four speed, dual plane Edelbrock manifold, and Holley 4 bbl would outpull my 1992 F150, 351, auto, FI engine and get better mileage doing it.

Course my 2004 Duramax/Allison crew cab puts them both to shame.

350 hp, 520 ft lbs torque, 18 mpg.  And will blow the doors off most any gas pickup...

[280plus]

Put a towing cam, 3" exhaust and compression in my 1990 E150 302 and it will pactically climb a wall now. Plenty of torque. The gas mileage is pathetic though.

[TarpleyG]

My son in law tells me that GM is working on a V6 Duramax for the half ton class for 2008 or '09.  Wouldn't that be a kick!

That's probably not a far stretch.  I have a 5 cylinder Vortec that puts out as much HP as my '89 5.0 Mustang did and nearly as much as my '98 M3 had.  Not too shabby for a mid-size P/U.  The new Tahoe with the small V-8 gets just about the same gas mileage as my Colorado and has 100 more HP.  That's technology only 3 years older than my truck.

Greg

[280plus]

I've got a 5.0 mustang motor in my 95 F-150. The thing WILL get up and go once the revs get up there but it won't pull worth a damn as far as I'm concerned. The truck is a dog when it's loaded. And once again, the gas mileage is pathetic. I have a 01 E-250 with the 5.4 (or whatever) and it's got plenty of power and gets about 14 mpg which ain't bad. Compared to the other 2. I'll get something on the order of 8.5 mpg in stop and go with the souped up 90 E-150. It'll do ~13 on the hwy. It IS loaded heavy though. I like driving it, it's got cohones. I love when it starts to open up, it's got that sound. And yes theres an aftermarket tranny cooler on it.

Incidentally I DO have to shift out of OD with all of them. They all have OD and every one will dog on a long hill. As soon as I start to feel them losing speed I shift down. The in and out you get when you leave them in auto4 is definitely not good for the tranny OR the motor.

One other thing. My brother the Ford mechanic calls the EO transmission the "E!! OH NO!!"transmission.

[Bogie]

Thanks, guys... I think it's time for a tune-up, new air filter, and a general debugging...
 
As for the vehicle I'd _really_ like for general use...
 
You guys know those Mercedes/Freightliner/Dodge vans that are out now? Taller and boxier than the Ford/Chevies...  They've got 5 cylinder turbo diesels in 'em, and get about 25mpg. One ton rear axle, some with duallies, but only about 5,000 pounds towing capacity (may be frame limited?).
 
I'd like to take that drive train/suspension, and put it under a pickup the size of a Dodge Dakota. Smaller frontal area, and you could tow a small fifth wheel.

[Brad Johnson]

I'm not real hip on the oiled gauze filters (e.g. K&N). They flow better, yes. But more flow is the result of less restriction, which is the result of larger pores in the filter media, which means less efficient filtering.

My brother got a K&N FIPK for his truck and it did run a little better, but the first time we popped the filter to clean it we found that the whole intake tract was coated in fine dust. Back in went the paper filter and no more dust problems.

There are also known problems with overoiled filters (which is very easy to do). The excess oil sheds off the filter as microscopic droplets which can deposit on the MAF sensor wires. The ones I've personally dealt with were easily cleaned with a spritz of zero residue electronics cleaner, but I've heard several first-hand accounts of failed sensors due to oil deposits.

As far as chips go, most of them make more power by richening the mixture slightly. Richer mixture equals worse economy.

I'd stick with what you have and concentrate on keeping things as tuned up as possible. If you have more than 80K on the clock, replace your TPS and O2 sensors even if you are not getting a fault code. Use all synthetic lubricants and pay attention to viscocity, it does make a difference. Go as light as possible while still maintaining wear resistance. Run good tires and remember that the vehicle mfg recommended tire pressure is usually a comprimise between wear, rolling resistance, and comfort. If you don't mind a slightly stiffer ride, putting an extra 3-5 psi will often return you a slight gain in economy. You can also run a taller tire - going from a 30" tall tire to a 33" tire is roughly the same as going from a 3.55 gear to a 3.20 gear. You might find a buddy with some taller tires and see if you could talk them into swapping for a weekend so you can try them out (or find a place that has a couple of good used tires you can buy cheap).

Brad

[Art Eatman]

Chevys generally benefit from better breathing, particularly with exhaust headers and relatively free-flow mufflers.

I'm not up on what can be done via a different chip; I'd suggest talking to the folks at a speed shop, moreso than just at a parts store.  Talk to the guys who install them, not the ones who just sell them.

When valve-job time comes, do some grinding on the inside of the curve of the ports.  Not hogging; just take that sharp edge from the casting, making a smooth rollover at that part of the port.

Gap the plugs maybe 0.005 tighter, and adjust the valves to one-half turn of lash instead of a full turn.

Puely opinion, but if one of these fancy air cleaners makes any obvious improvement, the old one was already way too dirty.

Art